Examples of comparators are shown in U.S. Pat. Nos. 4,384,219 and 4,529,891. In both cases a differential amplifier stage with two transistors is connected on the high potential side via a constant current source with a supply voltage source and on the low potential side via a current mirror with a ground lead.
The speed of a comparator is known to be higher the greater the bias current. That is, the speed at which an effect occurs at the comparator output when the input signal thereof passes through the comparator threshold depends on the strength of the bias current. From the point of view of the speed of the comparator it would therefore be desirable to supply a bias current with high current strength.
A high bias current leads to accordingly high power consumption, however, which is undesirable, especially when power is supplied from a battery. Conventionally, one must therefore make a compromise between a tolerable power consumption and a tolerable speed of the comparator. The invention addresses the problem of providing a comparator which is not subject to this compromise but permits both high speed and low power consumption.